Get a jump-start on managing plant pests
Just like us, insects spend their winters in different locations. Unlike us, they spend their winters in different stages of development. Some might overwinter as adults, others in their immature stage as grubs, caterpillars or nymphs, while others will be in the pupal stage like a chrysalis or cocoon.
Understanding their life cycle and location can help us support beneficial insects while managing problem insect pests.
Invite beneficial insects such as lady beetles, parasitic wasps and predatory mites to your landscape to help manage populations of plant-damaging pests. Add a birdbath to encourage insect-eating songbirds into your gardens. Most songbirds eat insects or feed them to their young while adding colour, movement and entertainment to your garden.
Keeping your plants healthy with proper care is the first important step in any pest management strategy. Healthy plants are better able to tolerate pest attacks and are more likely to recover from the damage.
Despite your best efforts, insect pests might attack and damage your plants. Birds and predaceous insects often manage small populations, but there might be times you decide to intercede. Winter is a great time to monitor and, in many cases, manage plant-damaging insects.
Scale insects can be one of these and come in a variety of colours and shapes, but all grow and reproduce under a waxy covering. This covering protects them from predators, desiccation and pesticides. Depending on the scale species they might overwinter as an immature scale, fertilized female or eggs under the protective covering.
Treating plant damaging scale in late winter or early spring is one way to jump-start control of this pest while having minimal or no impact on beneficial insects that will help manage this pest. Take some time now to check plants for problem pests such as the invasive oystershell scale.
This insect is not native to North America and is a pest of more than 130 species of plants including poplars, ash, beech, maple, willows, dogwood, cotoneaster and lilacs. Adult scale insects form a greyish to dark brown protective covering called a test that resembles an oyster or mussel shell. In the fall, the mated female lays 20 to 100 eggs inside the test, dies and the eggs remain there throughout the winter.
Removing heavily infected twigs and branches is an option when the scale population is contained in a small portion of the plant. You can also gently scrape the scale off branches and stems with a plastic dish scrubber. Be careful not to damage thinbarked plants.
Another option is to apply organic lightweight horticulture oil such as Summit Year-Round Spray Oil when plants are dormant. The temperatures must be 5 C or higher when treating. As always, read and follow label directions for effective and safe control.
Since the eggs are so well protected, a second application of the horticulture oil can increase success. Make a second application, if needed, when the eggs hatch and the immature insects known as crawlers emerge in spring after the buds have burst.
As you survey your landscape this winter, pay special attention to stressed plants and those susceptible to oystershell scale and other insect pests common in your area. Plants exposed to road dust and pesticides might also be more vulnerable as these conditions negatively impact predators and parasites that help manage plant pests.
Regularly monitoring plant health, working with nature and strategically managing invasive pests such as the oystershell scale can help improve the health, vigour and longevity of your landscape plants.
Melinda Myers has written more than 20 gardening books, including The Midwest Gardener’s Handbook and Small Space Gardening.